1. Field of the Invention
The present invention relates generally to implantable medical devices; and, more particularly, to a method and apparatus to automatically identify multiple leads and their proper connection to an implantable medical device such as a pacemaker or cardioverter/defibrillator.
2. Background Art
An implantable intravascular lead assembly is often implanted within a patient""s body to provide electrical stimulation to the heart. Such lead assemblies may include one or more electrical conductors that are adapted to be suitably connected to a source of electrical energy, which may be a pacemaker or cardioverter/defibrillator. The electrical conductor, in turn, includes an electrode tip that engages the endocardial or epicardial tissue of the heart to provide stimulation and sensing capabilities. The lead assembly may be intravenously inserted through a body vessel, such as a vein, into one or more cardiac chambers, or alternatively, attached to the epicardial surface of the heart. The conductor is sealed from body fluids by a biocompatible and bio-stable insulating material.
In a typical lead assembly, the electrode tip is firmly lodged in, and permanently secured to, the endothelial lining or epicardial surface of the heart. These lead assemblies are referred to as an endocardial or epicardial lead, respectively. Some examples of conventional endocardial and epicardial leads may be found in U.S. Pat. No. 3,348,548 to Chardack, U.S. Pat. No. 3,754,555 to Schmitt, U.S. Pat. No. 3,814,104 to Irnich et al., U.S. Pat. No. 3,844,292 to Bolduc, U.S. Pat. No. 3,974,834 to Kane, U.S. Pat. No. 5,246,014 to Williams, and U.S. Pat. No. 5,397,343 to Smits. A representative defibrillation lead is described in U.S. Pat. No. 6,178,355 to Williams.
With the increased use of multi-chamber pacemakers and defibrillators such as those that provide bi-atrial or bi-ventricular pacing capabilities, multiple leads are required to deliver electrical stimulation to various locations within the heart. With the use of multiple leads that are positioned within one or more small vessels of the body, it has become even more important to minimize lead and lead connector size. As leads become smaller, it becomes increasingly difficult to mark leads with the appropriate identification, including manufacturer identification and/or lead model and serial numbers. This may make it more difficult for a physician to determine which lead is to be inserted into a given port of an implantable medical device (IMD) during an implant procedure.
One solution to providing marking information on lead systems is described in U.S. Pat. No. 5,824,030 to Yang. This patent discloses a single-pass transvenous lead for atrial sensing and pacing, ventricular sensing and pacing, as well as for ventricular and atrial defibrillation. Visual indicators are provided on the lead to identify which one of several distal electrode pairs are being used.
Another solution to properly configuring the leads of an IMD is disclosed in U.S. Pat. No. 5,374,279 to Duffin. The described medical electrical pulse generator includes a switchable connector assembly. The connector assembly is provided with connector bores that are each adapted to receive a medical electrical lead. Electrical connectors located within the bores are arranged such that interconnection of the pulse generator circuitry and the configuration of the electrodes on the leads and/or housing of the device can be altered by means of connector pins.
Yet another method of attaching multiple electrode leads to an IMD is described in U.S. Pat. No. 4,628,934 to Pohndorf. The ""934 patent describes an electronic electrode switching circuit that minimizes the number of feedthroughs from a pacer case to a pacer neck that are needed to couple to the pacing lead electrodes. These feedthroughs can be selectively connected to a desired electrode by the physician at the time of initial implantation or any time thereafter. The electronic connection to a feedthrough may be dedicated to a single electrode or electrode pair, or alternatively, the electrodes may be electronically sampled by circuitry in the pacer. The electrode switching circuit may be located in the pacer neck, in an adapter between the pacer neck and a multielectrode lead, or in a multielectrode lead.
Another method for automatically configuring the multiple leads of an IMD is described in U.S. Pat. No. 6,085,118 to Hirschberg. The ""118 patent describes an implantable cardiac stimulator with at least two terminals. Each terminal is connectable to an implantable electrode for delivering stimulation pulses to a heart, and/or for sensing cardiac activity signals. The stimulator also has a switch and a control unit which operates the switch, so that one or both terminals are connectable to the pulse generator. The control unit identifies a position status for at least one of the electrodes in response to a signal received at the time of implantation. Although the control unit may use a signal from an electrode to configure the switch, premature sensed events, artifacts and/or EMI may cause the control unit to incorrectly configure the system.
Another identification system is described in U.S. Pat. No. 5,300,120 to Knapp, which involves a passive transponder that may be encoded with a binary value that may be up to sixty-four bits long. This value may be read with a hand-held electromagnetic device that is located outside the body and in proximity to the transponder. The encoded information may include patient demographics, implant data, and manufacturer information.
Another similar mechanism for remotely monitoring device data is described in U.S. Pat. No. 5,626,630 to Markowitz. The disclosed telemetry system includes a remote monitoring station, a repeater worn externally by a patient, and a quasipassive transponder attached to a device implanted in the patient. The remote monitoring station communicates to the repeater to initiate an interrogation routine between the repeater and the transponder to extract patient condition information from the implanted device. When the repeater receives the condition information, it relays it to the remote monitoring station. The disclosed system does not automatically identify leads, calibrate lead-based sensors, or automatically configure leads and/or sensors to an IMD.
U.S. Pat. No. 5,833,603 to Kovacs describes another system for sensing one or more physiological signals within a living body to measure optical, mechanical, chemical, and/or electrochemical properties. The system includes a transponder for wirelessly transmitting data corresponding to the sensed parameter values to a remote reader. Disclosed embodiments utilize temperature sensors, strain sensors, pressure sensors, magnetic sensors, acceleration sensors, ionizing radiation sensors, acoustic wave sensors, chemical sensors, and photosensors. The disclosed system does not include means to automatically identify or configure leads, or to calibrate the lead-based sensors.
Another mechanism for identifying information related to the configuration of an IMD is disclosed in U.S. Pat. No. 5,423,334 to Jordan. The disclosed system provides a characterization tag for attachment to the IMD. The tag circuitry is selectively loaded to store data describing the IMD, and may be read by a probe located outside the body. The system does not store lead identification or configuration information.
Yet another system for storing and transmitting device information is described in U.S. Pat. No. 5,252,962 to Urbas. The disclosed device includes a sensor for use in transmitting a parameter such as temperature from within a living body to a device that is located outside the body. The IMD includes a programmable memory to store user ID data.
While the above publications teach various improvements to the art, they do not address the problem of identifying and configuring multiple leads and/or other implantable devices for use with an IMD.
It is a principal object of the present invention to provide an improved interface between conventional lead systems and IMDs.
Another object is to provide a system and method for automatically identifying leads and for enabling the proper connection of the identified leads to an IMD.
Another object is to provide a system and method for automatically receiving sensor calibration information for lead-based sensors.
Yet another object is to provide a system and method for automatically calibrating lead-based sensors.
Another object is to provide an IMD that automatically configures connections between one or more leads and respective IMD ports.
An additional object is to provide a connector block for electrically and mechanically coupling multiple leads or sensors to an electrical source of energy, such as a pacemaker, defibrillator or neuro stimulator.
Yet another object is to provide a system for use with an IMD that allows an additional component of the IMD to be automatically identified for purposes of system configuration.
It is a further object to provide a system for use with an IMD that stores patient data that may be transferred to a central location for use in performing diagnosis and therapy.
The current system and method addresses these and other objectives by providing a system for use with an active IMD (hereinafter, xe2x80x9cIMDxe2x80x9d) such as a pacing device, or another external device. The system is capable of automatically identifying one or more additional implantable medical devices such as leads that may be associated with the IMD. In one embodiment, the invention includes a first communication circuit that is attached to, or integrated within, a lead. The communication circuit stores data such as model and serial numbers, technical information, and calibration data. At the time of implant or sometime thereafter, information stored by the first communication circuit may be transferred to a second communications circuit that is external to the lead. The second communications circuit may reside within the IMD, an external programmer, a personal data management (PDM) unit, or within any other unit such as a Personal Digital Assistant (PDA) that is located within a predetermined range of the first communication circuit. This transferred data can be used both to indicate the presence of the lead, and to identify lead type. Such information can be used, for example, to automatically configure the connector block of the IMD to properly couple to the lead. The data can further be used to automatically adjust amplifier gains or other circuitry associated with the lead. The data may be entered into a patient record on an external programmer, or may be transferred to a central storage location for use by health care providers when performing diagnosis and therapy associated with the IMD.
In another embodiment, the data provided by the first communications circuit includes identification and calibration information concerning additional components of the system. For example, physiologic sensors carried on the leads may be identified so that the IMD can enable and calibrate internal circuitry to receive the physiologic signals. This allows certain functions within the IMD to automatically be enabled only when a component is present in the system so that power can otherwise be conserved. Any other components of an IMD may be identified and calibrated by using a communication circuit according to the current invention. This may include implantable devices such as pluggable antennas, electrodes that can be selectively coupled to the IMD case, and any other types of components that may be selectively added to the system.
According to one aspect of the system, the first communication circuit may be a passively-powered RF transponder. The transponder receives power from an external source. Ultrasonic, optical, and electromagnetic power may be used to power the first communication circuit. In another embodiment, the first communication circuit may receive power from its host unit, such as via the conductors of a lead. According to another aspect of the system, the first communication circuit may include a receiver as well as a transmitter to receive data signals from an external source. This allows the first communication circuit to be programmed with identification, calibration, and other data at the time of component manufacture.